Microbial Biocatalysis

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Biocatalysis".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 40676

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Special Issue Editors

State Key Laboratory of Microbial Metabolism, School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China
Interests: microbial transformation; bioprocess engineering
Special Issues, Collections and Topics in MDPI journals
Jiangxi Province Key Laboratory of Mining and Metallurgy Environmental Pollution Control, School of Resource and Environmental Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China
Interests: biocatalysis and biodegradation; bioavailability of hydrophobic organic compounds; environmental stress and microbial metabolic response
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Biocatalysis is a sustainable alternative for the chemical industry in manufacturing, monitoring, and waste management. Biocatalytic processes perform with isolated enzymes or whole cells as biocatalysts. Whole-cell biocatalysts offer some unique advantages of cascade reactions catalyzed by multienzymes as well as a single bioredox reaction with cofactor regeneration in a single strain. Therefore, whole-cell biocatalysts are widely applied for biosynthesis/biotransformation to produce value-added chemicals as well as the complete mineralization of organic pollutants.

Biological catalytic processing using whole-cell biocatalysts includes biocatalyst engineering, bio-reaction engineering, and downstream processing. In addition to the traditional screening of microbial strains and immobilized whole-cell biocatalysts, modern genetic engineering, metabolic engineering, and synthetic biology make tailored whole-cell biocatalysts possible. At the same time, some integrated processes have successfully been applied in the catalytic processing using living whole-cell biocatalyst, such as harnessing biocompatible chemistry to interface with the microbial metabolism as well as using various separation techniques for in situ product removal.

The purpose of this Special Issue is to collect original research papers and reviews, focusing on progress using living whole-cell biocatalysts in biosynthesis, biotransformation, and biodegradation.

Dr. Zhilong Wang
Dr. Tao Pan
Guest Editor

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Keywords

  • Whole-cell biocatalyst, immobilized cells, genetic engineering, metabolic engineering, synthetic biology;
  • Bio-reaction engineering, fermentation, interfacial biocatalysis, biocompatible chemistry, chemo-enzymatic cascade reaction, designing bioreactor, process optimization;
  • Separation engineering, integrated processes, in situ product removal, extractive fermentation;
  • Biosynthesis, industrial enzymes, antibody, biosurfactant, biopigments, bioflavors, biofuels, bio-based materials, bioactive chemicals;
  • Biotransformation, drug intermediate, chiral chemical, value-added chemical;
  • Biodegradation, crude oil, aromatic hydrocarbon, plasticizer, environmental hormone, microplastic, bio-desulfurization

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Published Papers (16 papers)

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Editorial

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3 pages, 181 KiB  
Editorial
Microbial Biocatalysis
by Tao Pan and Zhilong Wang
Catalysts 2023, 13(3), 629; https://doi.org/10.3390/catal13030629 - 21 Mar 2023
Cited by 1 | Viewed by 1492
Abstract
Biocatalysis, which can be performed by whole cells and isolated enzymes, has become a topic of public interest for its potential use in the chemical industry in manufacturing, monitoring, and waste management [...] Full article
(This article belongs to the Special Issue Microbial Biocatalysis)

Research

Jump to: Editorial, Review

11 pages, 1347 KiB  
Article
Highly Efficient Biosynthesis of Nicotinic Acid by Immobilized Whole Cells of E. coli Expressing Nitrilase in Semi-Continuous Packed-Bed Bioreactor
by Xue-Jiao Liu, Bao-Di Ma, Xiao-Mei Wu and Yi Xu
Catalysts 2023, 13(2), 371; https://doi.org/10.3390/catal13020371 - 08 Feb 2023
Cited by 2 | Viewed by 1440
Abstract
A recombinant E. coli, expressing nitrilase from Acidovorax facilis 72W with dual-site expression plasmid pRSFduet (E. coli pRSF-AfNit2), was constructed. It showed higher soluble expression of nitrilase than that in the pET21a plasmid. The recombinant nitrilase can efficiently catalyze the hydrolysis [...] Read more.
A recombinant E. coli, expressing nitrilase from Acidovorax facilis 72W with dual-site expression plasmid pRSFduet (E. coli pRSF-AfNit2), was constructed. It showed higher soluble expression of nitrilase than that in the pET21a plasmid. The recombinant nitrilase can efficiently catalyze the hydrolysis of 3-cyanopyridine to nicotinic acid. The whole cells of E. coli pRSF-AfNit2 were immobilized by using sodium alginate/glutaraldehyde/polyethylene imine as the best immobilized reagents. The immobilized cells showed 95% activity recovery and excellent mechanical strength, with improved thermal stability and pH stability. They also retained 82% of initial activity after nearly two months of storage at 4 °C. A semi-continuous packed-bed bioreactor (sPBR) filled with the immobilized cells was studied for efficient production of nicotinic acid. After optimization, the highest space–time yield of 1576 g/(L·d) was obtained on 0.8 M substrate concentration at 2 mL/min of flow rate. The sPBR was repeatedly operated for 41 batches, keeping 100% conversion in the presence of 30 mM CaCl2. Finally, 95 g of nicotinic acid were obtained at 90% yield after separation and purification. The developed technology has potential application value. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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13 pages, 3078 KiB  
Article
7α and 7β Hydroxylation of Dehydroepiandrosterone by Gibberella sp. and Absidia Coerulea Biotransformation
by Ming Song, Ruicheng Fu, Sulan Cai, Xuliang Jiang, Fuju Wang, Weizhuo Xu and Wei Xu
Catalysts 2023, 13(2), 272; https://doi.org/10.3390/catal13020272 - 25 Jan 2023
Cited by 1 | Viewed by 1077
Abstract
The hydroxylation of dehydroepiandrosterone (DHEA) to 7α -hydroxy-5-androstene-17-one (7α-OH-DHEA) and 7β-hydroxy-5-androstene-17-one (7β-OH-DHEA) by Gibberella sp. CICC 2498 and Absidia coerulea CICC 41050 was investigated. The media ingredients were optimized. Single factors such as the DHEA concentration, culture time, medium volume, and inoculum rate [...] Read more.
The hydroxylation of dehydroepiandrosterone (DHEA) to 7α -hydroxy-5-androstene-17-one (7α-OH-DHEA) and 7β-hydroxy-5-androstene-17-one (7β-OH-DHEA) by Gibberella sp. CICC 2498 and Absidia coerulea CICC 41050 was investigated. The media ingredients were optimized. Single factors such as the DHEA concentration, culture time, medium volume, and inoculum rate were individually investigated to generate optimum biotransformation conditions. An orthogonal optimization process using a four-factor, three- level L9 (33) experiment was designed and performed. Finally, the maximum production of 7β-OH-DHEA from DHEA biotransformation by Absidia coerulea is 69.61%. This strategy would provide a possible way to enhance the 7β-OH-DHEA yield in the pharmaceutical industry. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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11 pages, 2381 KiB  
Article
Nysfungin Production Improvement by UV Mutagenesis in Streptomyces noursei D-3-14
by Ming Song, Wubing He, Sulan Cai, Fuju Wang, Weizhuo Xu and Wei Xu
Catalysts 2023, 13(2), 247; https://doi.org/10.3390/catal13020247 - 21 Jan 2023
Cited by 2 | Viewed by 1354
Abstract
Streptomyces noursei D-3-14 was taken as a starting strain and treated with UV (15 W, 30 cm) mutagenesis for 40 s for three consecutive rounds. High yielding strains were screened using chemical and biological potency determination, and the components of the fermentation products [...] Read more.
Streptomyces noursei D-3-14 was taken as a starting strain and treated with UV (15 W, 30 cm) mutagenesis for 40 s for three consecutive rounds. High yielding strains were screened using chemical and biological potency determination, and the components of the fermentation products were detected using HPLC. Finally, the mutant strain Streptomyces noursei 72-22-1 with a chemical potency of 8912 (U/mL) and a biological potency of 5557 (U/mL) was obtained after the genetic stability evaluation. After optimization of the fermentation conditions, the chemical potency and biological potency of Streptomyces noursei 72-22-1 reached 14,082 U/mL and 10579 U/mL, respectively, which is 1.58 and 1.91 times those before optimization. HPLC analysis indicated that the mutant strain 72-22-1 displayed a higher content of polyfungin B. When equimolar nystatin A1, A3, and polyfungin B were tested for their fungicidal activities towards Saccharomyces cerevisiae ATCC 2061, polyfungin B exhibited a better efficacy than nystatin A1 and A3. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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11 pages, 2547 KiB  
Article
Identification of New Amylolytic Enzymes from Marine Symbiotic Bacteria of Bacillus Species
by Mohammad Reza Erfanimoghadam and Ahmad Homaei
Catalysts 2023, 13(1), 183; https://doi.org/10.3390/catal13010183 - 13 Jan 2023
Cited by 2 | Viewed by 1968
Abstract
α-amylases are one of the most common and important industrial enzymes widely used in various industries. The present study was conducted with the aim of isolating and identifying symbiotic α-amylase enzyme-producing bacteria in the intestine of Silago Sihama and Rasterliger Canagorta fish living [...] Read more.
α-amylases are one of the most common and important industrial enzymes widely used in various industries. The present study was conducted with the aim of isolating and identifying symbiotic α-amylase enzyme-producing bacteria in the intestine of Silago Sihama and Rasterliger Canagorta fish living in Qeshm Island, Hormozgan. The intestinal symbiotic bacteria of these species were isolated using nutrient agar culture medium; then, α-amylase producing bacteria were screened using a special culture medium containing starch and the Lugol’s solution test. The α-amylase enzyme activity of enzyme-producing bacteria was measured using the starch substrate. Finally, bacteria with the highest enzyme activity were selected and identified by the 16S rRNA gene sequence analysis. The results showed that out of 22 isolated bacteria, 10 were able to grow in a special culture medium, and 5 strains of these 10 bacteria had the ability to produce relatively stronger halos. The four bacterial strains belonging to the genus Bacillus that had the highest α-amylase enzyme activity were identified and registered in the NCBI gene database as B. subtilis strains HR13, HR14, HR15, and HR16. Among these four strains, two strains of B. subtilis, HR13 and HR16, displayed high enzyme activity and maximum activity at 60 °C at pH values of 5 and 7, respectively. α-Amylase enzymes isolated from marine symbiotic bacteria of Bacillus species can be considered potential candidates for application in various industries. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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12 pages, 2993 KiB  
Article
Correlation Relationship between Phase Inversion of Pickering Emulsions and Biocatalytic Activity of Microbial Transformation of Phytosterols
by Wenyu Zhao, Haisheng Xie, Xuehong Zhang and Zhilong Wang
Catalysts 2023, 13(1), 72; https://doi.org/10.3390/catal13010072 - 30 Dec 2022
Cited by 1 | Viewed by 1288
Abstract
Microbial transformation of hydrophobic phytosterols into the pharmaceutical steroid precursors AD (androst-4-ene-3, 17-dione) and ADD (androst-4-diene-3, 17-dione) in a water–plant oil two-phase system by Mycolicibacterium neoaurum is a paradigm of interfacial biocatalysis in Pickering emulsions stabilized by bacterial cells. In the present work, [...] Read more.
Microbial transformation of hydrophobic phytosterols into the pharmaceutical steroid precursors AD (androst-4-ene-3, 17-dione) and ADD (androst-4-diene-3, 17-dione) in a water–plant oil two-phase system by Mycolicibacterium neoaurum is a paradigm of interfacial biocatalysis in Pickering emulsions stabilized by bacterial cells. In the present work, phase inversion of Pickering emulsions—i.e., Pickering emulsions turning from water-in-oil (W/O) emulsions into oil-in-water (O/W) ones—was observed during microbial transformation in the presence of high concentrations of crystal phytosterols. It was found that there is a correlation relationship between the phase behaviors of Pickering emulsions and the biocatalytic activity of utilizing M. neoaurum as a whole-cell catalyst. Efficient microbial transformation under the high crystal phytosterol loadings was achieved due to the formation of O/W emulsions where interfacial biocatalysis took place. Under the optimal conditions (volume ratio of soybean oil to water: 15:35 mL, phytosterols concentration in the soybean oil: 80 g/L, glucose as co-substrate in the aqueous culture medium: 10 g/L), the concentrations of AD and ADD reached 4.8 g/L based on the whole broth (16 g/L based on the oil phase) after microbial transformation for 9 days. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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12 pages, 1952 KiB  
Article
An O-Demethylation Metabolite of Rabeprazole Sulfide by Cunninghamella blakesleeana 3.970 Biotransformation
by Ming Song, Hongxiang Zhu, Jian Wang, Weizhuo Xu and Wei Xu
Catalysts 2023, 13(1), 15; https://doi.org/10.3390/catal13010015 - 22 Dec 2022
Cited by 2 | Viewed by 1765
Abstract
To explore the potential metabolites from rabeprazole sulfide, seven strains of filamentous fungi were screened for their biotransformation abilities. Among these strains, Cunninghamella blakesleeana 3.970 exhibited the best result. Four different culture media were screened in order to identify the most optimal for [...] Read more.
To explore the potential metabolites from rabeprazole sulfide, seven strains of filamentous fungi were screened for their biotransformation abilities. Among these strains, Cunninghamella blakesleeana 3.970 exhibited the best result. Four different culture media were screened in order to identify the most optimal for subsequent research. Single factors such as the initial pH of culture media, culture time, inoculation volume, and media volume were individually investigated to provide the optimum biotransformation conditions. Then, an orthogonal optimization process using a five-factor, four-level L16(45) experiment was designed and performed. Finally, when the substrate concentration is 3 g/L, one major metabolite was detected with a transformation rate of 72.4%. Isolated by semipreparative HPLC, this metabolite was further detected by ESI-MS and NMR. The final data analysis indicated that the metabolite is O-demethylation rabeprazole sulfide. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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14 pages, 3025 KiB  
Article
Enhancement of α-Ketoglutaric Acid Production by Yarrowia lipolytica Grown on Mixed Renewable Carbon Sources through Adjustment of Culture Conditions
by Ludwika Tomaszewska-Hetman, Anita Rywińska, Zbigniew Lazar and Waldemar Rymowicz
Catalysts 2023, 13(1), 14; https://doi.org/10.3390/catal13010014 - 22 Dec 2022
Cited by 3 | Viewed by 1501
Abstract
α-Ketoglutaric acid (KGA) is a valuable compound with a wide range of applications, e.g., in the cosmetics, pharmaceutical, chemical and food industries. The present study aimed to enhance the efficiency of KGA production by Yarrowia lipolytica CBS146773 from renewable carbon sources. In the [...] Read more.
α-Ketoglutaric acid (KGA) is a valuable compound with a wide range of applications, e.g., in the cosmetics, pharmaceutical, chemical and food industries. The present study aimed to enhance the efficiency of KGA production by Yarrowia lipolytica CBS146773 from renewable carbon sources. In the investigation, various factors that may potentially affect KGA biosynthesis were examined in bioreactor cultures performed on a simple medium containing glycerol (20 g/L) and fed with four portions of a substrate mixture (15 + 15 g/L of glycerol and rapeseed oil). It was found that the process may be stimulated by regulation of the medium pH and aeration, application of selected neutralizing agents, supplementation with thiamine and addition of sorbitan monolaurate, whereas presence of biotin and iron ions had no positive effect on KGA biosynthesis. Adjustment of the parameters improved the process efficiency and allowed 82.4 g/L of KGA to be obtained, corresponding to productivity of 0.57 g/L h and yield of 0.59 g/g. In addition, the production of KGA was characterized by a low level (≤6.3 g/L) of by-products, i.e., citric and pyruvic acids. The results confirmed the high potential of renewable carbon sources (glycerol + rapeseed oil) for effective KGA biosynthesis by Yarrowia lipolytica. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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12 pages, 2289 KiB  
Article
Biodegradation of Crystalline and Nonaqueous Phase Liquid-Dissolved ATRAZINE by Arthrobacter sp. ST11 with Cd2+ Resistance
by Jiameng Zhang, Zhiliang Yu, Yaling Gao, Meini Wang, Kai Wang and Tao Pan
Catalysts 2022, 12(12), 1653; https://doi.org/10.3390/catal12121653 - 15 Dec 2022
Cited by 3 | Viewed by 982
Abstract
A newly isolated cadmium (Cd)-resistant bacterial strain from herbicides-polluted soil in China could use atrazine as the sole carbon, nitrogen, and energy source for growth in a mineral salt medium (MSM). Based on 16S rRNA gene sequence analysis and physiochemical tests, the bacterium [...] Read more.
A newly isolated cadmium (Cd)-resistant bacterial strain from herbicides-polluted soil in China could use atrazine as the sole carbon, nitrogen, and energy source for growth in a mineral salt medium (MSM). Based on 16S rRNA gene sequence analysis and physiochemical tests, the bacterium was identified as Arthrobacter sp. and named ST11. The biodegradation of atrazine by ST11 was investigated in experiments, with the compound present either as crystals or dissolved in di(2-ethylhexyl) phthalate (DEHP) as a non-aqueous phase liquid (NAPL). After 48 h, ST11 consumed 68% of the crystalline atrazine in MSM. After being dissolved in DEHP, the degradation ratio of atrazine was reduced to 55% under the same conditions. Obviously, the NAPL-dissolved atrazine has lower bioavailability than the crystalline atrazine. Cd2+ at concentrations of 0.05–1.5 mmol/L either had no effect (<0.3 mmol/L), slight effects (0.5–1.0 mmol/L), or significantly (1.5 mmol/L) inhibited the growth of ST11 in Luria-Bertani medium. Correspondingly, in the whole concentration range (0.05–1.5 mmol/L), Cd2+ promoted ST11 to degrade atrazine, whether crystalline or dissolved in DEHP. Refusal to adsorb Cd2+ may be the main mechanism of high Cd resistance in ST11 cells. These results may provide valuable insights for the microbial treatment of arable soil co-polluted by atrazine and Cd. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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16 pages, 1612 KiB  
Article
Metabolic Pathway of Phenol Degradation of a Cold-Adapted Antarctic Bacteria, Arthrobacter sp.
by Gillian Li Yin Lee, Nur Nadhirah Zakaria, Hiroyuki Futamata, Kenshi Suzuki, Azham Zulkharnain, Noor Azmi Shaharuddin, Peter Convey, Khadijah Nabilah Mohd Zahri and Siti Aqlima Ahmad
Catalysts 2022, 12(11), 1422; https://doi.org/10.3390/catal12111422 - 12 Nov 2022
Cited by 12 | Viewed by 2277
Abstract
Phenol is an important pollutant widely discharged as a component of hydrocarbon fuels, but its degradation in cold regions is challenging due to the harsh environmental conditions. To date, there is little information available concerning the capability for phenol biodegradation by indigenous Antarctic [...] Read more.
Phenol is an important pollutant widely discharged as a component of hydrocarbon fuels, but its degradation in cold regions is challenging due to the harsh environmental conditions. To date, there is little information available concerning the capability for phenol biodegradation by indigenous Antarctic bacteria. In this study, enzyme activities and genes encoding phenol degradative enzymes identified using whole genome sequencing (WGS) were investigated to determine the pathway(s) of phenol degradation of Arthrobacter sp. strains AQ5-05 and AQ5-06, originally isolated from Antarctica. Complete phenol degradative genes involved only in the ortho-cleavage were detected in both strains. This was validated using assays of the enzymes catechol 1,2-dioxygenase and catechol 2,3-dioxygenase, which indicated the activity of only catechol 1,2-dioxygenase in both strains, in agreement with the results from the WGS. Both strains were psychrotolerant with the optimum temperature for phenol degradation, being between 10 and 15 °C. This study suggests the potential use of cold-adapted bacteria in the bioremediation of phenol pollution in cold environments. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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8 pages, 2597 KiB  
Article
Production of Trans-Cinnamic and p-Coumaric Acids in Engineered E. coli
by Yuqi Liu, Weizhuo Xu and Wei Xu
Catalysts 2022, 12(10), 1144; https://doi.org/10.3390/catal12101144 - 30 Sep 2022
Cited by 4 | Viewed by 1667
Abstract
Trans-cinnamic acid and p-coumaric acid are valuable intermediates in the synthesis of flavonoids and are widely employed in food, flavor and pharmaceutical industries. These products can be produced by the deamination of L-phenylalanine and L-tyrosine catalyzed by phenylalanine ammonia lyase or [...] Read more.
Trans-cinnamic acid and p-coumaric acid are valuable intermediates in the synthesis of flavonoids and are widely employed in food, flavor and pharmaceutical industries. These products can be produced by the deamination of L-phenylalanine and L-tyrosine catalyzed by phenylalanine ammonia lyase or tyrosine ammonia lyase. Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) from Rhodotorula glutinis do not exhibit strong substrate specificity and can convert both L-phenylalanine and L-tyrosine. In this study, the PAL was utilized as the whole-cell biocatalyst, and the reaction conditions were optimized, and the production of trans-cinnamic acid and p-coumaric acid of 597 mg/L and 525 mg/L were achieved with high purity (>98%). Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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10 pages, 2354 KiB  
Article
Enhancing Acetophenone Tolerance of Anti-Prelog Short-Chain Dehydrogenase/Reductase EbSDR8 Using a Whole-Cell Catalyst by Directed Evolution
by Hui Zhang, Bei Wang, Shengli Yang, Hongwei Yu and Lidan Ye
Catalysts 2022, 12(9), 1071; https://doi.org/10.3390/catal12091071 - 19 Sep 2022
Cited by 2 | Viewed by 1474
Abstract
The short-chain dehydrogenase/reductase (SDR) from Empedobacter brevis ZJUY-1401 (EbSDR8, GenBank: ALZ42979.1) is a promising biocatalyst for the reduction of acetophenone to (R)-1-phenylethanol, but its industrial application is restricted by its insufficient tolerance to acetophenone. In this paper, we developed a chromogenic [...] Read more.
The short-chain dehydrogenase/reductase (SDR) from Empedobacter brevis ZJUY-1401 (EbSDR8, GenBank: ALZ42979.1) is a promising biocatalyst for the reduction of acetophenone to (R)-1-phenylethanol, but its industrial application is restricted by its insufficient tolerance to acetophenone. In this paper, we developed a chromogenic reaction-based high-throughput screening method and employed directed evolution to enhance the acetophenone tolerance of EbSDR8. The resulting variant, M190V, showed 74.8% improvement over the wild-type in specific activity when catalyzing the reduction of 200 mM acetophenone. Kinetic analysis revealed a 70% enhancement in its catalytic efficiency (kcat/Km). Molecular docking was conducted to reveal the possible mechanism behind the improved acetophenone tolerance, and the result implied that the M190V mutation is conducive to the binding and release of coenzyme. Aside from the improved catalytic performance when dealing with a high concentration of acetophenone, other features of M190V, such as a broad pH range (6.0 to 10.5), low optimal cosubstrate concentration (1% isopropanol), and a temperature optimum close to that of E. coli cells (35 °C), also contribute to its practical application as a whole-cell catalyst. In this study, we first designed a directed evolution means to engineer the enzyme and obtained the positive variant which has a high activity under high concentrations of acetophenone. After that, we optimized the catalytic performance of the variant to adapt to industrial applications. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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13 pages, 4137 KiB  
Article
C058 and Other Functional Microorganisms Promote the Synthesis of Extracellular Polymer Substances in Mycelium Biofloc
by Yiyong Li, Wanyi Luo, Wen Liu, Yongcong Yang, Zexiang Lei, Xueqin Tao and Baoe Wang
Catalysts 2022, 12(7), 693; https://doi.org/10.3390/catal12070693 - 24 Jun 2022
Cited by 2 | Viewed by 1305
Abstract
The mycelium biofloc bioaugmented by Cordyceps strain C058 effectively purifies water, which may be related to the synthesis of extracellular polymer substances. To verify this conjecture, we analyzed the changes in extracellular polymer substances content in the mycelium biofloc under various hydraulic retention [...] Read more.
The mycelium biofloc bioaugmented by Cordyceps strain C058 effectively purifies water, which may be related to the synthesis of extracellular polymer substances. To verify this conjecture, we analyzed the changes in extracellular polymer substances content in the mycelium biofloc under various hydraulic retention times (36 h, 18 h, and 11 h). The microstructure and microflora composition were analyzed using a scanning electron microscope and high-throughput sequencing. The ordinary biofloc without bioaugmentation was taken as a control. The results showed that under the above hydraulic retention time, the extracellular polymer substances contents of the mycelium biofloc were 51.20, 55.89, and 33.84 mg/g, respectively, higher than that of the ordinary biofloc (14.58, 15.72, and 18.19 mg/g). The protein content or the polysaccharide content also followed the same trend. Meanwhile, the sedimentation performance of the mycelium biofloc was better than that of the ordinary biofloc, attributed to the content of the extracellular polymer substances. It is worth noting that C058 is the main biofloc content, which promotes the synthesis of extracellular polymer substances in the mycelium biofloc. Other functional microorganisms in the mycelium biofloc were Janthinobacterium, Phormidium, Leptolyngbya, Hymenobacter, and Spirotrichea, which also promote the synthesis of extracellular polymer substances. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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Review

Jump to: Editorial, Research

21 pages, 1501 KiB  
Review
Multifunctional Enzymes in Microbial Secondary Metabolic Processes
by Jun-Tao Wang, Ting-Ting Shi, Lin Ding, Juan Xie and Pei-Ji Zhao
Catalysts 2023, 13(3), 581; https://doi.org/10.3390/catal13030581 - 14 Mar 2023
Cited by 2 | Viewed by 1778
Abstract
Microorganisms possess a strong capacity for secondary metabolite synthesis, which is represented by tightly controlled networks. The absence of any enzymes leads to a change in the original metabolic pathway, with a decrease in or even elimination of a synthetic product, which is [...] Read more.
Microorganisms possess a strong capacity for secondary metabolite synthesis, which is represented by tightly controlled networks. The absence of any enzymes leads to a change in the original metabolic pathway, with a decrease in or even elimination of a synthetic product, which is not permissible under conditions of normal life activities of microorganisms. In order to improve the efficiency of secondary metabolism, organisms have evolved multifunctional enzymes (MFEs) that can catalyze two or more kinds of reactions via multiple active sites. However, instead of interfering, the multifunctional catalytic properties of MFEs facilitate the biosynthetic process. Among the numerous MFEs considered of vital importance in the life activities of living organisms are the synthases involved in assembling the backbone of compounds using different substrates and modifying enzymes that confer the final activity of compounds. In this paper, we review MFEs in terms of both synthetic and post-modifying enzymes involved in secondary metabolic biosynthesis, focusing on polyketides, non-ribosomal peptides, terpenoids, and a wide range of cytochrome P450s(CYP450s), and provide an overview and describe the recent progress in the research on MFEs. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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17 pages, 10627 KiB  
Review
Diclofenac Biodegradation by Microorganisms and with Immobilised Systems—A Review
by Danuta Wojcieszyńska, Karolina Łagoda and Urszula Guzik
Catalysts 2023, 13(2), 412; https://doi.org/10.3390/catal13020412 - 15 Feb 2023
Cited by 10 | Viewed by 2535
Abstract
Diclofenac is one of the most popular non-steroidal anti-inflammatory drugs. Due to its over-the-counter availability and high consumption along with municipal and hospital wastewater, it enters the sewage treatment plant, where it is not completely degraded. This results in the appearance of diclofenac [...] Read more.
Diclofenac is one of the most popular non-steroidal anti-inflammatory drugs. Due to its over-the-counter availability and high consumption along with municipal and hospital wastewater, it enters the sewage treatment plant, where it is not completely degraded. This results in the appearance of diclofenac in the effluents from the treatment plant, and with them, it enters the surface waters. Due to its structure, it is characterised by its high resistance to degradation in the environment. At the same time, it shows documented acute and chronic toxicity to non-target organisms. For this reason, it is necessary to look for cheap solutions that enhance the degradation of diclofenac. The paper discusses both the pathways of microbiological degradation of this drug described so far, as well as modern systems of biocatalyst immobilisation, with a particular emphasis on laccases involved in the biotransformation of diclofenac. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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14 pages, 1192 KiB  
Review
Biodegradation of Different Types of Bioplastics through Composting—A Recent Trend in Green Recycling
by Wazir Aitizaz Ahsan, Adnan Hussain, Chitsan Lin and Minh Ky Nguyen
Catalysts 2023, 13(2), 294; https://doi.org/10.3390/catal13020294 - 28 Jan 2023
Cited by 17 | Viewed by 14225
Abstract
In recent years, the adoption of sustainable alternatives has become a powerful tool for replacing petroleum-based polymers. As a biodegradable alternative to petroleum-derived plastics, bioplastics are becoming more and more prevalent and have the potential to make a significant contribution to reducing plastic [...] Read more.
In recent years, the adoption of sustainable alternatives has become a powerful tool for replacing petroleum-based polymers. As a biodegradable alternative to petroleum-derived plastics, bioplastics are becoming more and more prevalent and have the potential to make a significant contribution to reducing plastic pollution in the environment. Meanwhile, their biodegradation is highly dependent on their environment. The leakage of bioplastics into the environment and their long degradation time frame during waste management processes are becoming major concerns that need further investigation. This review highlights the extent and rate of the biodegradation of bioplastic in composting, soil, and aquatic environments, and examines the biological and environmental factors involved in the process. Furthermore, the review highlights the need for further research on the long-term fate of bioplastics in natural and industrial environments. The roles played by enzymes as biocatalysts and metal compounds as catalysts through composting can help to achieve a sustainable approach to the biodegradation of biopolymers. The knowledge gained in this study will also contribute to the development of policies and assessments for bioplastic waste, as well as provide direction for future bioplastics research and development. Full article
(This article belongs to the Special Issue Microbial Biocatalysis)
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